Sound scattering by marine organisms was studied off the
Oregon coast and between Hawaii and Adak, Alaska. Variations in
scattering were observed over a period of several hours, over did
(24-hour) periods, from month to month, from inshore to offshore,
in relation to biomass of midwater animals, and temperature and
salinity.
Usually one or two scattering layers migrated vertically, ascending
or descending at dusk and dawn respectively. At times
reflectors migrated between surface waters and upper scattering
layers during twilight periods. No statistical difference was found
between rates of ascent and descent because of the variability in
rates of migration that was observed.
The amount or thickness of scattering in the water column
was found to vary from day to night and with seasons. There was a
general trend for more scattering during night than day, yet it was
not statistically significant. Seasonally, more scattering appeared
to be present during the summer in some years but not in others.
Surface scattering varied not in amount but in the type present during
different seasons and between day and night.
Geographically, scattering was found in smaller amounts in
offshore than inshore waters of Oregon. Variations in scattering
were noted among the water masses between Hawaii and Adak,
Alaska. Geographic changes in scattering and biomass showed a
positive correlation between euphausiid catches and the amount of
scattering. However, euphausiids are not considered the only group
scattering sound.
The great amount of variability in scattering is discussed. It
may be due to differences in the species causing scattering and
variability in the behavior of individual species, possibly resulting
from changes in light and temperature. / Graduation date: 1968
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28213 |
| Date | 01 September 1967 |
| Creators | Donaldson, Henry Adam |
| Contributors | Pearcy, William G. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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